I had an event last night after powering up the Masso, when taking out of Estop the Z plunged. Not didn’t know what was going on so I hit the Estop. When resetting watched the Z plunge again about 3/4”. Looking at the stepper the driver the lights were flashing back and forth between the red and green one. Powered it down did the cable wiggle thing, tried again and this time the Z moved up. Powered down again, unplugged and re-plugged in the cable and it resolved the issue.
So my PSA would be to make sure you park your machine high enough and it’s clear below the spindle before taking out of estop.